The part played by the palsies of children in the surgical affections of the extremities necessitates a short description of their more important features.
#Anterior poliomyelitis# is the lesion underlying what was formerly known as _infantile paralysis_--a name to be avoided, because the condition is not confined to infants and it is not the only form of paralysis met with in young children. Anterior poliomyelitis is characterised by an illness attended with fever, in which the child is found to have lost the power of one, less frequently of both lower extremities; or, it may be, of one or both arms. After a period, varying from six weeks to three months, the paralysis tends to diminish both in extent and degree, and in the majority of cases it ultimately persists only in certain muscles or groups of muscles. At the onset of the paralysis the affected limb is helpless and relaxed, the reflexes are lost, the muscles waste, and those that are paralysed exhibit the reaction of degeneration. In severe cases, and especially if proper treatment is neglected, the nutrition of the limb is profoundly affected; its temperature is subnormal, the skin is bluish in cold weather and readily becomes the seat of pressure sores. In course of time the limb lags behind its fellow in growth, and tends to assume a deformed attitude, which at first can easily be corrected, but later becomes permanent.
[Illustration: FIG. 127.--Female child showing the results of Poliomyelitis affecting the left lower extremity; the limb is short and poorly developed, the pelvis is tilted and the spine is curved.]
When the acute stage of the illness is past, the chief question is to what extent recovery of function can be looked for in the paralysed muscles.
It would appear to be established that if a muscle reacts to faradism it will recover, but the contrary proposition does not follow. It was formerly accepted that a muscle which exhibits the reaction of degeneration is incapable of recovery, but observation has shown that this is not the case. Complete destruction of the motor cells in the anterior horn of grey matter as a result of poliomyelitis is now known to be exceptional; as a matter of fact, damage to the nerve cells is usually capable of being repaired. The muscles governed by these cells may appear to be completely paralysed, but with appropriate treatment their functional activity can be restored. As functional disability is frequently due to the affected muscle being _over-stretched_, it is of the first importance, when the acute symptoms are on the wane, that every care should be taken to prevent the weak muscular groups being put upon the stretch, and the greatest attention should be paid to _the posture of the limb during convalescence_. For example, if the child is allowed to lie with the wrist flexed, the flexor muscles undergo shortening, and the extensors are over-stretched and are therefore placed at a mechanical disadvantage. As the inflammatory changes in the anterior horn of the cord subside, the flexor tendons, from their position of advantage, are in a condition to respond to the first stimuli that come from their recovering motor cells, while the extensors are not in a position to do so. If, on the other hand, the wrist and fingers are maintained in the attitude of extreme dorsiflexion, the extensors become shortened, and, relieved of strain, they soon begin to respond to the stimuli sent them from the recovering nerve cells. Similarly in the lower extremity, when, for example, the muscles innervated through the peroneal (external popliteal) nerve are paralysed, if the foot is allowed to remain in the attitude of inversion with the heel drawn up--paralytic equino-varus--an attitude which is rendered more pronounced by the pressure of the bedclothes, the chance of the muscles recovering their function is seriously diminished. Another potent factor in preventing recovery, especially in the lower limbs, is _erroneous deflection of the body weight_. If, for example, there is weakness in the tibial group of muscles, and the child is allowed to walk, the eversion of the foot will steadily increase, the tibial muscles will be more and more stretched, the opposing peroneal muscles will shorten, and, in time, the bones of the tarsus will undergo structural alterations which will perpetuate the deformity. If, on the other hand, by some alteration of the boot, the foot is maintained in the attitude of inversion, the weakened or paralysed tibial muscles are placed in a much more favourable condition for recovery.